Cyclic total parenteral nutrition (C-TPN) is a widely used infusion therapy for providing nutrition to patients who are not able to extract nutrition from food in a normal manner. One great advantage of C-TPN is that, by concurrently infusing a solution of dextrose, amino acids and fat, the C-TPN therapy need not be continuous. Thus, this therapy permits an improved quality of life for the patient by allowing him or her to resume normal daytime activities. As implied, C-TPN is indicated for patients, both young and old, who still require long-term parenteral nutrition, but who have demonstrated they can function for extended periods of time without receiving infused fluids.
As might be expected, a cyclical therapy which is accomplished by periodically initiating and terminating IV infusions needs to be administered in a manner which allows the body's metabolic processes to properly adjust to the infusions. Such an adjustment may be necessary either at the beginning of the infusion or at the end of the infusion. C-TPN is certainly no exception. It typically happens that C-TPN requires stabilization of the body's metabolic processes at both the initiation and the termination of each infusion session in the therapy. Specifically, with C-TPN it is necessary to avoid hyperglycemia in the early stages of the infusion process, and to avoid hypoglycemia during the final stages of the process. To avoid these conditions, C-TPN is normally started with a gradual increase in the rate at which fluid is infused to the patient, and is ended with a gradual decrease in this rate.
The problems with C-TPN therapy concerning hyperglycemia and hypoglycemia have been known for some time. The general response to overcome these problems has been to somehow taper the initiation and the termination of the therapy. Indeed, several methods have been suggested for these purposes. Another problem, which has been less prominent, concerns the actual profiling of an infusion therapy regime which is optimally suited for the particular patient. For example, pediatric patients will require different infusion regimens than will adult patients. And geriatric patients may require yet another regimen. This problem is particularly acute where C-TPN is to be administered using relatively expensive infusion pumps. Each case will be different and, consequently, it may be necessary to reprofile the infusion regimen. Flexibility, then, is key.
Some apparatus and methods for accomplishing C-TPN therapy using infusion pumps have been suggested. For example, U.S. Pat. No. 4,758,799 which issued to Schoon et al. for an invention entitled "Method and Apparatus for Automatic Profiled Infusion in Cyclic TPN" establishes an infusion regimen, or cycle profile, which begins at a set starting infusion rate and which has an appropriate steady-state rate and appropriate tapers in accordance with pre-established criteria when total volume and total infusion time per cycle are entered. The disclosure of the Schoon et al. patent, however, does not address the problem confronted when a patient is unable to handle the set starting infusion rate which, as is disclosed for Schoon et al., is about 60 ml/hr. Further, the disclosure of Schoon et al. requires an upward taper and a downward taper which, other than their start and end points, are effectively identical. In short, there is little flexibility in profiling the infusion regimen. Another example, though perhaps less sophisticated than the Schoon et al. disclosure, is a method wherein the infusion rate during the tapering periods is one half the maintenance rate. Such a method is disclosed in an article entitled "Cyclic Total Parenteral Nutrition" by Bennett and Rosen, Nutrition in Clinical Practice 5:163-165, 1990.
In light of the above, it is an object of the present invention to provide a system and method for infusing C-TPN fluids to a patient which is an efficacious therapy for the patient who requires C-TPN. Another object of the present invention is to provide a system and method for infusing C-TPN fluids to a patient which is adaptable for use by either a pediatric, an adult, or a geriatric patient. Still another object of the present invention is to provide a system and method for infusing C-TPN fluids to a patient which allows the user to adjust the infusion regimen to meet the specific needs of the particular patient. Yet another object of the present invention is to provide a system and method for infusing C-TPN fluids to a patient which, with selected input data, automatically profiles an infusion regimen which insures an enhanced accuracy. Another object of the present invention is to provide a system for infusing C-TPN fluids to a patient which is simple to use, relatively easy to manufacture, and comparatively cost effective.